Amorphous soft magnetic materials, such as Fe, Co or Ni base amorphous magnetic alloys have been widely used in the fabrication of various magnetic components, for example magnetic saturable cores, high frequency transformers and current transducer cores. Recently soft magnetic materials having higher initial permeability and reduced core loss have been required in the manufacturing of scaled-down and high frequency power supplies. Usually amorphous soft magnetic shaped materials are subjected to annealing at a temperature below their crystallization temperature to eliminate the internal stress thereof so as to improve their magnetic properties, in particular the initial permeability and core loss characteristics. The annealing treatment can be conducted without applying a magnetic field or can be conducted in a static magnetic field, applied either in the direction the amorphous soft magnetic shaped materials are magnetized, i.e., so-called longitudinal-field annealing; or in a direction generally perpendicular to the magnetized direction, so-called transverse-field annealing.
U.S. Pat. No. 4,944,805 issued to Kanji Nakanishi discloses a method of heat treating amorphous soft magnetic film layers. The method involves performing a heat treatment after each amorphous soft magnetic(ASM) film has been deposited on a substrate, at a temperature lower than the crystallization temperature and the Curie temperature of the ASM film in a static magnetic field applied either in a direction generally perpendicular to the direction in which a high magnetic permeability for high frequency is to be finally attained in the ASM film or in the principle direction in which the high permeability for high frequency is desired; performing a heat final treatment, after all of the layers of ASM films have been deposited, at a temperature equal to or lower than the temperature for the previous treatment in a static magnetic field applied either in the principle or in a direction generally perpendicular thereto. The purpose of the heat treatment is to reduce magnetic anisotropy.
U.S. Pat. No. 5,114,503 issued to Yoshihito Yoshizawa et al discloses magnetic cores which are obtained by being subjected to a heat treatment at a temperature between a crystallization temperature and a curie temperature, and then to a heat treatment at a temperature less than the curie temperature by about 50.degree. C. in a magnetic field in the direction of the magnetic path of the core. The magnetic cores thus treated have a higher rectangular ratio and a reduced stress relief ratio.